Method and apparatus for improving the utility of a automatic dependent surveillance

ABSTRACT

The surveillance system provides a means to augment Automatic Dependent Surveillance-Broadcast (ADS-B) with “look alike ADS-B” or “pseudo ADS-B” surveillance transmissions for aircraft which may not be ADS-B equipped. The system uses ground based surveillance to determine the position of aircraft not equipped with ADS-B, then broadcasts the identification/positional information over the ADS-B data link. ADS-B equipped aircraft broadcast their own position over the ADS-B data link. The system enables aircraft equipped with ADS-B and Cockpit Display of Traffic Information (CDTI) to obtain surveillance information on all aircraft whether or not the proximate aircraft are equipped with ADS-B.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of U.S. patentapplication Ser. No. 09/516,215, filed on Feb. 29, 2000, which in turnclaims priority from Provisional Application Ser. No. 60/123,170, filedMar. 5, 1999, both of which are incorporated herein by reference in itsentirety.

[0002] The subject matter of the present application is related to thefollowing issued U.S. Patents, assigned to the same assignee as thepresent invention, all of which are incorporated herein by reference intheir entirety:

[0003] U.S. Pat. No. 6,049,304, issued Apr. 11, 2000, entitled “Methodand Apparatus for Improving the Accuracy of Relative Position EstimatesIn a Satellite-Based Navigation System”;

[0004] U.S. Pat. No. 5,999,116, issued Dec. 7, 1999, entitled “Methodand Apparatus for Improving the Surveillance Coverage and TargetIdentification in a Radar Based Surveillance System”;

[0005] U.S. Pat. No. 6,094,169, issued Jul. 25, 2000, entitled “PassiveMultilateration Auto-Calibration and Position Error Correction”;

[0006] U.S. Pat. No. 6,384,783, issued on May 7, 2002, entitled “Methodand Apparatus for Correlating Flight Identification Data With SecondarySurveillance Radar Data”;

[0007] U.S. Pat. No. 6,211,811, issued Apr. 2, 2001, entitled “Methodand Apparatus for Improving the Surveillance Coverage and TargetIdentification in a Radar Based Surveillance System”;

[0008] U.S. Pat. No. 6,448,929, issued Sep. 10, 2002, entitled “Methodand Apparatus for Correlating Flight Identification Data With SecondarySurveillance Radar Data”; and

[0009] U.S. Pat. No. 6,567,043, issued May 20, 2003, entitled “METHODAND APPARATUS FOR IMPROVING THE UTILITY OF AUTOMATIC DEPENDENTSURVEILLANCE”.

[0010] In addition, the subject matter of the present application isrelated to that in the following U.S. Patent Applications:

[0011] U.S. patent application Ser. No. 10/319,725, filed Dec. 16, 2002,entitled “VOICE RECOGNITION LANDING FEE BILLING SYSTEM”, incorporatedherein by reference in its entirety; and

[0012] Provisional U.S. Patent Application No. 60/440,618, filed Jan.17, 2003, incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0013] The present invention relates to the field of aircraftsurveillance and monitoring, particularly toward a technique known asAutomatic Dependent Surveillance.

BACKGROUND OF THE INVENTION

[0014] The Automatic Dependent Surveillance-Broadcast (ADS-B) concepthas been introduced as a means to enhance future ground and avionicsbased surveillance of aircraft. This concept is defined in MinimumAviation System Performance Standards for Automatic DependentSurveillance Broadcast (ADS-B), RTCA/DO-186, February 1998, which islater referred to as ADS-B MASPS and is incorporated herein byreference. The ADS-B concept provides for aircraft and ground vehiclesto periodically broadcast their state vector (horizontal and verticalposition, horizontal and vertical velocity) and other information.

[0015] A specific implementation of a 1090 MHz based ADS-B system isdescribed in Drouilhet et al., U.S. Pat. No. 5,570,095, issued Oct. 29,1996 and incorporated herein by reference. The broadcast ADS-B messageprovides surveillance information to other users, principally AirTraffic Control (ATC) and aircraft/vehicle operators.

[0016] Applications for ADS-B include ATC display of traffic, runwayincursion detection and alerting, and Cockpit Display of TrafficInformation (CDTI). One example of CDTI is a map-like display centeredon a pilot's aircraft showing relative positions and intentions of otherproximate aircraft. Another example of CDTI is provided in Buchanan etal., U.S. Pat. No. 4,196,474, issued Apr. 1, 1980, also incorporatedherein by reference.

[0017] The Federal Aviation Administration (FAA) and the NationalAeronautics and Space Administration (NASA) have investigated thesuitability of this technology to support these applications in theairport surface environment. NASA recently tested ADS-B using 1090 MHzdata transmission in an airport surface environment as part of the LowVisibility Landing and Surface Operations (LVLASO) program. Tests havebeen performed to assess how well 1090 MHz ADS-B performs with respectto surveillance system requirements established by the InternationalCivil Aviation Organization (ICAO) and RTCA.

[0018] Two issues were identified during ADS-B system implementation andtesting at Atlanta Hartsfield International Airport (ATL) as describedin “Application of ADS-B for Airport Surface Surveillance”, Dan Hicok,Derrick Lee, 17^(th) Digital Avionics System Conference, November, 1998:

[0019] 1. A method may be required for CDTI equipped aircraft to obtainsurveillance information on aircraft and ground vehicles which are notequipped with ADS-B.

[0020] 2. Loss of ADS-B surveillance may occur due to multipath,blockage, and antenna pattern nulls.

[0021] Aircraft equipped with ADS-B and CDTI receive surveillanceinformation directly from ADS-B transmissions. ADS-B implementation mayrequire installation of new avionics equipment. There may inevitably bea transition period when some aircraft are ADS-B equipped and otheraircraft are not. ADS-B MASPS has defined a means to augment ADS-B witha Traffic Information Services (TIS) data link, whereby ground basedsurveillance information for all aircraft is transmitted to CDTI capableaircraft.

[0022] An example of a TIS implementation may be found in Crow, U.S.Pat. No. 5,627,546, issued May 6, 1997, and incorporated herein byreference. Two sources of TIS traffic information are secondarysurveillance radar and multilateration, as described in Schwab, U.S.Pat. No. 5,528,244, issued Jun. 18, 1996, and Alsup et al., U.S. Pat.No. 5,191,342, issued Mar. 3, 1993, both of which are incorporatedherein by reference. A TIS data link was implemented at ATL for testing.A major limitation of TIS is the implementation may require aircraftowners to purchase a second data link in addition to the ADS-B link.

[0023] ATL testing also showed obstructions and multipath fromstructures may result in degradation or total loss of directaircraft-to-aircraft ADS-B surveillance. The airport surface environmentmay be particularly challenging due to the presence of large structures,such as concourses and hangars. Loss of surveillance and degradedsurveillance negatively impacts the ability of a pilot to maintainsituational awareness of arrivals, departures and runway occupancy.

[0024] Accordingly, what is needed is a new method to augment the ADS-Bconcept using the ADS-B data link to provide surveillance informationfor aircraft and ground vehicles which are not equipped with ADS-B. Thisnew method needs to provide a means to reinforce ADS-B transmissionswhich are adversely impacted by the environment.

SUMMARY OF THE INVENTION

[0025] The present invention provides an improved apparatus and methodfor use with Automatic Dependent Surveillance-Broadcast (ADS-B). In amethod and apparatus of the present invention, each ADS-B equippedaircraft may periodically broadcast its position as derived from itsnavigation system.

[0026] Aircraft with ADS-B receivers may then be able to receive thesebroadcasts to obtain the location of proximate ADS-B equipped aircraft.The invention provides a means to augment ADS-B transmissions withposition and identification information of aircraft which may not beADS-B equipped.

[0027] In addition, the present invention reinforces ADS-B transmissionsin areas where line-of-sight or multipath issues prevent reliable ADS-Bcommunications between two aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a diagram depicting “pseudo” ADS-B augmentation ADS-Bconcept using SSR Surveillance.

[0029]FIG. 2 is a diagram depicting “pseudo” ADS-B augmentation ADS-Bconcept using Multilateration Surveillance.

[0030]FIG. 3 is a diagram depicting a 1090 MHz ADS-B format.

[0031]FIG. 4 is a diagram depicting “pseudo” ADS-B reinforcement ofADS-B transmissions.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention is now described with reference to theaccompanying Figures where like reference numbers denote like element orsteps.

[0033] In the preferred embodiment, a “pseudo” ADS-B ground systemcomprising one or more 1090 MHz remote receiver/transmitters 100 and acentral workstation 170 may be used to provide a source for 1090 MHz“pseudo” ADS-B transmissions 110, as illustrated in FIG. 1. 1090 MHz“pseudo” ADS-B transmissions 110 serve to augment 1090 MHz ADS-Btransmission 140 thus providing ADS-B/CDTI equipped aircraft 120 with acomplete picture of all proximate aircraft 130, 160.

[0034] As defined by the ADS-B concept [RTCA ADS-B MASPS], aircraftequipped with ADS-B 130, 120 periodically broadcast their own positioninformation via ADS-B transmission. In the preferred embodiment theseADS-B transmissions may be performed using an aircraft transponderfrequency of 1090 MHz. ADS-B/CDTI equipped aircraft 120 receive anddecode these 1090 MHz ADS-B transmissions 140 to obtain positioninformation on proximate ADS-B equipped aircraft 130.

[0035] The 1090 MHz “pseudo” ADS-B ground system provides ADS-B/CDTIequipped aircraft 120 with periodic 1090 MHz ADS-B like broadcasttransmissions or 1090 MHz “pseudo” ADS-B transmissions 110 representingposition data for aircraft not equipped with ADS-B 160. While FIG. 1illustrates only one 1090 MHz remote receiver/transmitter 100 performing1090 MHz “pseudo” ADS-B transmissions 110, any or all 1090 MHz remotereceiver/transmitters 100 may broadcast 1090 MHz “pseudo” ADS-Btransmissions 110.

[0036] 1090 MHz remote receiver/transmitters 100 receives and decodes1090 MHz ADS transmissions 140 to identify and locate ADS-B equippedaircraft 120, 130. 1090 MHz remote receiver/transmitters 100 send ADS-Bsurveillance data 200 to central workstation 170. Central workstation170 receives target information 190 from Secondary Surveillance Radar(SSR) 150 and/or a 1090 MHz multilateration system to obtainsurveillance information for all transponder equipped aircraft 120, 130,including non-ADS-B aircraft 160.

[0037] All aircraft which are ADS-B equipped may have a transponder. NonADS-B aircraft may also be provided with a transponder. The transpondergenerates a radio signal identifying the aircraft (and optionallyproviding altitude or other data) either periodically, in response to aradar signal, or when “squawked” by the pilot or other operator of theaircraft.

[0038] Central workstation 170 correlates 1090 MHz ADS-B aircrafttargets to transponder equipped targets. Central workstation 170identifies transponder equipped targets which do not have acorresponding ADS-B position, thus may not be ADS-B equipped (e.g.,aircraft 160 in FIG. 1). Transponder identification and positioninformation for non-ADS-B equipped aircraft 210 may be sent to 1090 MHzremote receiver/transmitters 100 where it may be broadcasted via 1090MHz “pseudo” ADS-B transmissions 110.

[0039] One version of 1090 MHz ADS-B position report 140 format may bedefined in FIG. 3. Aircraft may be equipped with either a Mode S or anATCRBS transponder as defined in Minimum Operational PerformanceStandards for Air Traffic Control Radar Beacon System/Mode Select(ATCRBS/MODE S) Airborne Equipment, RTCA/DO-181A, January 1992. TheADS-B message address may be identical to the Mode S transponderaddress. Accordingly, the ADS-B address may be obtained directly fromthe Mode S address.

[0040] Some aircraft may be equipped with ATCRBS transponders, insteadof Mode S. The ATCRBS message contains a Mode A address, which may beused to generate a ADS-B address. One method to convert Mode A addressto ADS-B message address may be to apply an algorithm which converts anaircraft tail number (e.g., registration number or N-number) to a 24 bitaddress. Mode A address may be converted from the tail number obtainedby accessing flight plan information. In turn, the tail number may beconverted to a ADS-B address. This algorithm is presently used by theFederal Aviation Administration to assign newly installed Mode Stransponders with an address.

[0041] 1090 MHz remote receiver/transmitters 100 may generate “pseudo”ADS-B transmissions 110 for ground vehicles operating on an airportmovement area. Ground vehicle surface surveillance may be obtained froma primary radar or other surveillance means. The “pseudo” ADS-Btransmissions mimic the format and style of “real” ADS-B transmissions,and thus are indistinguishable to ADS-B equipment provided in anaircraft. The “pseudo” ADS-B transmission is created from secondaryaircraft location data (e.g., radar, multilateration, or the like) fornon-ADS-B equipped aircraft. An airplane receiving “pseudo” ADS-B dataprocesses such data in the same manner as “real” ADS-B data, and thuscan locate, using ADS-B equipment, non-ADS-B equipped aircraft (e.g.,aircraft 160).

[0042] As may be readily appreciated by one of ordinary skill in theart, the use of such “pseudo” ADS-B transmissions allows the ADS-Bsystem to be used even in situations where not all aircraft are ADS-Bequipped. Of course, non-ADS-B aircraft will still not be detected inareas where “pseudo” ADS-B transmission equipment is not located.However, the risk of collision and situations of heavy traffic usuallyoccur in major metropolitan and airport areas which can be readilyserved by such a “pseudo” ADS-B system.

[0043] An ADS-B augmentation using 1090 MHz multilateration as asurveillance source is illustrated in FIG. 2. Multilateration systemsreceive aircraft transponder transmissions 245 and apply Time Differenceof Arrival techniques to determine an aircraft position. A basicrequirement of a multilateration system may be to provide a Time ofArrival (TOA) measurement capability. An example of such amultilateration system is discussed in co-pending U.S. patentapplication Ser. No. 09/209,008, entitled “Passive MultilaterationAuto-Calibration and Position Error Correction”, incorporated herein byreference.

[0044] A plurality of 1090 MHz remote receiver/transmitters 210 with TOAmeasurement hardware provide a means to perform multilateration todetermine a position of aircraft not equipped with ADS-B 240. 1090 MHzremote receiver/transmitters 210 provide traffic information toADS-B/CDTI equipped aircraft 260 via “pseudo” ADS-B transmissions 250.

[0045] The “pseudo” ADS-B ground system provides a means to reinforce1090 MHz ADS-B transmissions 340 with 1090 MHz “pseudo” ADS-Btransmissions 310, as illustrated in FIG. 4. A system comprising acentral workstation 370 and a plurality of 1090 MHzreceiver/transmitters 300 and 305 provides diversity for both receivingADS-B messages 340 and transmitting “pseudo” ADS-B messages 310. FIG. 4illustrates a case where line-of-sight may be obstructed by a building350 between two ADS-B/CDTI equipped aircraft 330 and 320 operating onintersecting runways.

[0046] One aircraft may be designated as the source aircraft 330 and theother aircraft may be designated as the destination aircraft 320. Whensource aircraft 330 transmits a 1090 MHz ADS-B transmission 340, it maybe received by a 1090 MHz remote receiver/transmitter 300. Decoded ADS-Btransmission 380 may be sent to a central workstation 370. Centralworkstation 370 determines when another 1090 MHz ADS-B/CDTI equippedaircraft 320 may require traffic information reinforcement with decodedADS-B transmission 380.

[0047] Central workstation 370 routes message 330 to a remotereceiver/transmitter 305, which has line-of-sight with destinationaircraft 320. 1090 MHz remote receiver/transmitter 305 transmits areinforcing 1090 MHz “pseudo” ADS-B transmission 310. 1090 MHz “pseudo”ADS-B transmission 310 may be identical in content to 1090 MHz ADS-Btransmission 340 originating from source aircraft 330.

[0048] The system selects 1090 MHz remote receiver/transmitter 300, 305,which has line-of-sight and the highest probability of being received atthe destination aircraft. A test or multipath simulation may beperformed when the system may be first installed to determine, whichremote receiver/transmitter has the highest probability of transmissionreception success for each location of the movement area or airspace.

[0049] The main implementation of ADS-B may be through Mode S or 1090MHz datalink technology. Mode S message formats have been allocated forADS-B use. Note that, also, some implementations of ADS-B may use otherdatalinks (such as digital VHF, or TDMA-like formats). However, the sametechnology may be applied in the present invention regardless of thedatalink selected for use.

[0050] While the preferred embodiment and various alternativeembodiments of the invention have been disclosed and described in detailherein, it may be apparent to those skilled in the art that variouschanges in form and detail may be made therein without departing fromthe spirit and scope thereof.

We claim:
 1. An aircraft position location system for generatingposition data for a plurality of aircraft, the system comprising: meansfor receiving aircraft position data from a broadcast aircraft positionsystem; means for generating aircraft position data using data otherthan broadcast aircraft position system data; means for correlatingaircraft position data from the broadcast aircraft position system withaircraft position data from other than the broadcast aircraft positionsystem; means for generating broadcast aircraft position system data foraircraft not equipped with the broadcast aircraft position system fromaircraft position data generated using data other than the broadcastaircraft position system data; and means for transmitting the broadcastaircraft position system data to aircraft equipped with the broadcastaircraft position system such that aircraft equipped with the broadcastaircraft position system can determine locations of aircraft notequipped with the broadcast aircraft location position system.
 2. Theaircraft position location system of claim 1, wherein said means forreceiving aircraft position data from a broadcast aircraft positionsystem comprises means for receiving data from a plurality of AutomaticDependent Surveillance System-Broadcast (ADS-B) units on a plurality ofcorresponding aircraft, each ADS-B unit generating and transmittingposition data.
 3. The aircraft position location system of claim 1,wherein said means for receiving aircraft position data from a broadcastaircraft position system comprises means for receiving data from aground-based Automatic Dependent Surveillance System-Broadcast (ADS-B),each ADS-B unit generating and transmitting position data.
 4. Theaircraft position location system of claim 3, wherein said means forgenerating aircraft position data using data other than broadcastaircraft position system data comprises a ground-based broadcastaircraft position system operating with a predefined format notcompatible with a format of a ground-based Automatic DependentSurveillance System-Broadcast (ADS-B).
 5. The aircraft position locationsystem of claim 2, wherein said means for generating aircraft positiondata using data other than broadcast aircraft position system datacomprises a ground-based multilateration system.
 6. The aircraftposition location system of claim 4, wherein said means for correlatingaircraft position data from the broadcast aircraft position system withaircraft position data from other than the broadcast aircraft positionsystem comprises software running on a workstation for receiving ADS-Bdata and secondary surveillance radar data, and determining from thesecondary surveillance radar data and ADS-B data, which aircraft do nothave ADS-B units.
 7. The aircraft position location system of claim 5,wherein said means for correlating aircraft position data from thebroadcast aircraft position system with aircraft position data fromother than the broadcast aircraft position system comprises softwarerunning on a workstation for receiving ADS-B data and multilaterationdata, and determining from the multilateration data and ADS-B data,which aircraft do not have ADS-B units.
 8. The aircraft positionlocation system of claim 6, wherein said means for generating broadcastaircraft position system data for aircraft not equipped with thebroadcast aircraft position system comprises software running on theworkstation for generating an ADS-B format signal indicating position ofa detected aircraft not having an ADS-B unit.
 9. The aircraft positionlocation system of claim 7, wherein said means for generating broadcastaircraft position system data for aircraft not equipped with thebroadcast aircraft position system comprises software running on theworkstation for generating an ADS-B format signal indicating position ofa detected aircraft not having an ADS-B unit.
 10. The aircraft positionlocation system of claim 8, wherein said means for transmitting thebroadcast aircraft position system data for aircraft not equipped withthe broadcast aircraft position system comprises a transmitter, fortransmitting the ADS-B format signal indicating position of a detectedaircraft not having an ADS-B unit.
 11. The aircraft position locationsystem of claim 9, wherein said means for transmitting the broadcastaircraft position system data for aircraft not equipped with thebroadcast aircraft position system comprises a transmitter, fortransmitting the ADS-B format signal indicating position of a detectedaircraft not having an ADS-B unit.